Updates to comply with best practices for gem development outlined by Yehuda Katz...

...in his blog post, ["Clarifying the Roles of the .gemspec and Gemfile"](http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/).

Specifically, gems should not include the Gemfile.lock and dependencies should be specified in the gemspec.